Hybrid tube front end and transistor output stage

[Original Burnedfingers]

Hi

Any ideas on how to construct a transistor output stage with a minimum amount of parts and couple to a tube line stage or tube front end. I have found several Mosfet hybrid designs but I want to stay with TO-3 outputs like the Motorola MJ15024 and MJ15025.

Joe

[Pjotr]

have found several Mosfet hybrid designs but I want to stay with TO-3 outputs like the Motorola MJ15024 and MJ15025

Why?

I would go for something like a choke loaded source follower driven by a Mu stage if you don’t need lots of power. That is for sure a minimum of parts

Cheers

[grataku]

Have you seen this?
http://www.audiodesignguide.com/ba/gy50sh.jpg

[Original Burnedfingers]

quote:
have found several Mosfet hybrid designs but I want to stay with TO-3 outputs like the Motorola MJ15024 and MJ15025


Why?

To be honest I like transistors better and I like to use what I have on hand. No offense.

Pjotr

Thanks for the link. It looks like a triple darlington output stage but its kinda blurred and I can't see it all that well.

Joe

[djk]

'burnedfingers'

Hi Joe!

You will probably have to run a tripple with the MJ15024/25, unless you're driving it with a cathode follower like a Foreplay.

If you want to get fancy you could reverse the driver transistors so the tripple looks like the one in an Altec 9440A, McIntosh 2120, Ampzilla III, etc. This would cut down on the bias a bit too.

If you really slam a 6C45Pi at 30mA with a choke load you could do a double with the MJE15030/31 and MJ21193/94.

What were you thinking about for the front end?

[Original Burnedfingers]

Hi Dennis

I will see if I can post this line stage.

[Original Burnedfingers]

The power supply I actually used is different than this one. Since I don't have the ability to build a schematic and post it this is as close as I can get. My B+ is higher and the plate resistor is larger but bias is the same as this one.


Joe